Magnesium alloy for pistons



Patented Feb. 17, 1931 UNITED STATES PATENT OFFICE WALTHER SCHMIDT, OF BITTERFELD, GERMANY, ASSIGNOR 'IO I. G. FARBENIN- DUSTRIE AKTIENGESELLSCHAFT, OF 'FRANKFORT-ON-THE-MAIN, GERMANY," A COR- IPORA'J IION' OF GERMANY MAGNESIUM ALLOY FOR PISTONS No Drawing. Application filed July 5, 1928, Serial No. 290,706, and in Germany July 4, 1927.

In my co-pending application Serial No. 206,128, filed July 15, 1927, Ihave described high percentage alloys of magnesium containing, besides, aluminum and silicon. In these alloys the amount of silicon ranges from more than 1 up to 6% and the aluminum contents Varies from 6 to Owing to their hardness and small thermal dilatation combined with a comparatively high melting point,

1 these alloys have proved to be particularly suitable for piston bodies in internal combustion engines.

I have now found that the quality of these alloys may be still further improved by re- 15 placing part 01" the aluminum contained therein, by certain amounts of another metal, such as copper, zinc or cadmium, and even adding said metal in an amount exceeding the amount of aluminum, Without impairing the favorable properties of these alloys as set forth, and in certain cases even improving them. Also in these alloys, the high content in silicon has a hardening efi'ect' and, moreover, results in diminishing the coefficient of expansion by about 10%, an efiect which is of the utmost importance in pistons for internal combustion engines.

The total of the non-magnesium content,

silicon included, should not be more than 20 by Weight of the alloy and at the same time the amount of the alloying metals proper should be so determined as not to lower the melting point of the alloy below 400 0.,

this being the lower limit for qualifying the alloys for pistons in combustion engines.

In this' respect, I have found an alloy of magnesium, containing 2 percent ofaluminum, 15 percent of copper and 3 percent of silicon to be particularly adapted to the purose.

p In these alloys the alloying metals may be introduced in the form of their silicide compounds, although this is not imperative.

For this purpose, the necessary amount of the metallic silicide is finely crushed to powder and stirred into the molten metal at a temperature sufficiently high to prevent the magnesium-silicide, the formation of which takes place immediately, from crystall zing prematurely. Otherwise the magnes umtaining more than 1 but not more than. 6%

of silicon, a substantial amount of aluminum and also a substantial amount of a metal of the group consisting of copper, zinc and cadmium, the total of the two alloying metals proper ranging from about 6% upwards and the total of the alloying substances not exceeding 20% by weight of the alloy, the

balance being magnesium.

A high percentage magnesium alloy containing more than 1 butnot more than 6% of silicon, a substantial amount of aluminum and also a substantial amount of copper, the total of both aluminum and copper ranging from about 6% upwards and the total of the alloying substances not exceeding 20% by weight of the alloy, the balance being magnesium.

3. A high, percentage magnesium alloy containing 15% of copper, 2% of aluminum and 3% of silicon, the balance being magnesium.

4. A high percentage magnesium alloy for piston bodies in internal combustion engines, containing more than 1 but not more than 6% of silicon, a substantial amount of aluminum and also a substantial amount of a metal of the group consisting of copper, zinc and cadmium, the total of the two alloying metals proper ranging from about 6% upwards, but not sufficient to effect a lowering of the melting point of the alloy below e100 6 and the total of the alloying substances not exceeding 20% by weight of the alloy,- the balance being magnesium.

5. A high percentage magnesium alloy for piston bodies in internal combustion engines, containing more than 1 but not more than 6% of silicon, a substantial amount of aluminum and also a substantial amount of copper, the total of both aluminum and copper ranging from about 6% upwards, but not sufiicient to effect a lowering of the melting point of the alloy below 400 C. and the total of the alloying substances not exceeding 20% by weight of the alloy, the balance bein magnesium.

6. A piston body made of a 'gh percentage magnesium alloy containing more than 1 but not more than 6% of silicon, a substantial amount of aluminum and also a substantial amount of a metal of the group consisting of copper, zinc 'and cadmium, the total of the two alloying metals proper ranging from about 6% upwards, but not suificient to effeet a lowering of the melting point of the alloy below 400 (1, and the total of the alloying substances not exceedin 20% by Weight of the alloy, the balance eing magnesium. v

7. A piston body made of a high percentage magnesium alloy containing more than 1 but not more than 6% of silicon, a substantial" amount of aluminum and also a substantial amount of copper, the total of both aluminum and copper ranging from about 6% upwards, but not suflicient to eflect a lowering of the melting point of the alloy below 400 C, and the total of the alloying substances not e.\'- ceeding 20% by Weight of the alloy, the balance being magnesium.

8. A piston body made of a high percentage magnesium alloy containing 15% of copper, 2% of aluminum and 3% of silicon, the balance being magnesium.

In testimony whereof I have hereunto set my hand. WALTHER SCHMIDT. 

